The invention relates to machines for wrapping loads intended to wind, or, as those skilled in the art would say, to xe2x80x9cbanderollxe2x80x9d, a width of wrapping film, generally made of polyethylene, around these loads, from the bottom to the top, to protect them from dust and running moisture. These loads are generally placed on pallets.
Wrapping is performed either by rotating on a platform the load which pulls the width of film off a feed reel, being rolled up inside it, or by rotating an arm which pulls the width off the reel to wind it around the load. In any event, at the end of the wrapping cycle, the width has to be cut and welded at the bottom of the load using a cutting and welding gripper device.
As there may be a desire to wrap loads of different heights, the cutting and welding device with which wrapping machines are generally equipped is designed for minimal load height, and is therefore relatively short and often shorter than the breadth of the width of wrapping film on the feed reels. This is why wrapping machines are often also equipped with a so-called pleating device for adapting and reducing the breadth of the wrapping film upstream of the cutting and welding device, in the direction in which the width of film travels.
There are already known certain devices for pleating widths of films on wrapping machines comprising a frame, two freely rotating turn rolls, this being mounted so that it can pivot about a central axis of the frame perpendicular to its plane so as, with the width of film slipped between the two rolls of the frame, to twist it between two planes which are inclined with respect to one another by pivoting the frame and thus force the lateral edges of the width to slide towards each other against the rolls, towards the inside of the frame, in a pleating movement that reduces the edge-to-edge breadth.
Such pleating devices do, however, display drawbacks.
First of all, pivoting the pleating frame requires a certain amount of travel which increases the space required by the machine.
Secondly, and above all, as the lower lateral edge of the width moves closer to the axis of pivoting of the frame during pleating, and as it is thus moved upwards, the pleating device and the reel holder need to be lowered in order to be truly able to weld and cut at the base of the load, and this is also detrimental to the space required by the machine.
The present invention aims to alleviate these drawbacks.
To this end, it relates to a load wrapping machine for winding a width, with a top lateral edge and a bottom lateral edge of a reel of wrapping film around the load, comprising a reel holder, means for winding the width around the load, a device for cutting and welding the width and a device for pleating the width of film, this device being intended to bring the two lateral edges of the width closer together, the machine being characterized in that the pleating device is designed to bring the two lateral edges of the width closer together simply by sliding the top lateral edge downwards.
Thus, and by virtue of the invention, as the heightwise position of the bottom lateral edge of the width of wrapping film is not altered by the pleating device, the width can easily be cut and welded at the base of the load.
In the preferred embodiment of the machine of the invention, the pleating device comprises a distancing bar mounted articulated at its base and means for making the bar pivot on its base.
By inclining the bar about its base, its top part, or top, is distanced from the vertical through its base, distancing with it the top lateral edge of the width of film thus forcing the top portion of width adjacent to the top lateral edge, to slide along the distancing bar towards its base, that is to say downwards.
As a preference, the distancing bar is mounted so that it is free to rotate on itself.
As the width of film continues to pass through the pre-stretching and pleating device and the pivoting of the distancing bar distances the width of film gradually from the bottom upwards, and therefore gives rise to a speed gradient on the speed at which the width travels around the distancing bar, from the nominal speed of travel near the bottom of the bar to a maximum speed near the top lateral edge, it is advantageous for the distancing bar to comprise a number of portions which rotate independently of one another to prevent the top part of the width from rolling up on itself and forming a twist.
Still in a best attempt at avoiding the formation of twists, it is preferable for the distancing bar to comprise, towards its top, friction means intended to apply relative retention to the width of film, for example projections, asperities, roughnesses, raised striations.